1. Field of the Invention
The invention relates to screw and cap mechanisms with particular application to forming collapsible tube dispensers.
2. Background Information
The earliest collapsible tube dispensers in the US patent database date from the early nineteenth century. Since that time, there has been continued innovation, leading to the various collapsible tube dispensers used for pharmaceuticals, personal care products, toothpaste, foods, artist's paints, glues, hazardous chemicals, grease products and viscous plastics, to name some of the more common uses of these tubes. As used herein, personal care products include, but are not limited to, cosmetics, facial care products, skin care products, and/or hair care products.
There are problems with the collapsible tube technologies of the prior art. They do not lend themselves both to being reusable and supporting the complete, controlled dispensing of their contents. As the term is used herein, reusable will refer to the capability to dispense small, or controlled, portions of the contents multiple times, perhaps on different occasions. Reusable may further refer to the capability to refill the contents multiple times. And reusable may further refer to a container, which can be cleaned, and refilled with differing contents.
One prior art collapsible tube dispenses all the tube's contents and is reuseable. The tube is not cylindrical but a two-sided pouch of soft plastic material. The tube has a mechanism of closing the throat, requiring no conventional screw and cap. The throat contains a soft plastic sheet insert that effectively sucks itself closed when pressure is released. This tube may be limited to applications in which there is no unexpected or forceful pressure applied to the tube. Example applications where it is not applicable include being packed in a suitcase, or purse, since the closure responds to finger pressure. The tube may also be limited to applications in which a high degree of barrier to the environment is not critical, such as pharmaceuticals, because the opening does not clean itself when closing except to the degree that it draws contents outside the tube to the inside of the tube. It may be undesirable for personal care products or other products demanding a high degree of aesthetic features, such as oversized caps allowing the tube to stand vertically.
There are some one-time use containers made essentially of a squeeze tube with a narrow end, which is cut to open the tube. All of the contents are then squeezed out, and the tube is discarded. These one-time use containers are not reusable, and represent a significant amount of overhead both for the manufacturer and for the ecology of people and systems, which must cope with these discarded containers.
With the exception of some one-time use containers, collapsible tube dispensers typically possess a rigid shoulder and a rigid throat. The rigid throat provides an exterior, rigid screw. This exterior rigid screw mates with a cap providing a matching interior screw pattern. When the cap is screwed onto the exterior screw of the throat, a seal is formed, which seals in the contents of the collapsible tube.
For the last century or two, screws have been built with either threads that taper away from the body, or remain of constant thickness. These screw threads will be referred to herein as open threads. Up until now, using these open thread screws requires that the throat of a collapsible tube be essentially rigid. An essentially rigid throat on a collapsible tube dispenser virtually guarantees that some of the tube contents will not readily leave the tube, causing the tube to waste some of its contents. The rigid shoulder further guarantees this waste.
The use of tubes for carrying food in sports and wilderness exploration environments is well-known. None on the market, however, are both reusable and completely collapsible. Thus, they do not dispense all their contents. A refillable tube that does dispense all its contents is especially desirable when food is otherwise scarce.
FIG. 1A shows a prior art exterior screw 20 with a prior art external thread form 22. The prior art external thread form 22 is shown in an expanded view through the following examples shown in FIGS. 1B and C with a matching internal thread form 24.
There is a local coordinate system in FIG. 1A, which will be used throughout this document. The z axis 10 extends through the center of the cylinder of the prior art exterior screw 20, and is the central axis of the cylinder. The r axis 12 is the radial direction of the thread at a point, which, for the sake of discussion, is referred to as thread point 22 in FIG. 1A. The n axis 14 is normal to the thread point 22. When the screw is turned in the n direction, it engages more of the threads.
The engagement of an exterior screw thread and matching interior screw is shown in the expanded view of the prior art open screw thread 22 in FIG. 1A. The expanded view is a cross-section of the threads taken in the plane of the z axis 10 and the r axis 12.
FIG. 1B shows an example of FIG. 1A using a standard acme thread for the external thread form 22 and the matching internal thread form 24. A first external acme thread 22-1 matches the first internal acme thread 24-1. A second external acme thread 22-2 with the second internal acme thread 24-2.
FIG. 1C shows an example of FIG. 1A using a standard buttress thread for the external thread form 22 and the matching internal thread form 24. A first external buttress thread 22-3 matches the first internal buttress thread 24-3. A second external buttress thread 22-4 with the second internal buttress thread 24-4.
FIG. 1D shows an example of FIG. 1A using a box thread for the external thread form 22 and the matching internal thread form 24. A first external box thread 22-5 matches the first internal box thread 24-5. A second external box thread 22-6 with the second internal box thread 24-6.
One skilled in the art will recognize that FIGS. 1B to 1D show some of the many variations in open threads in use today. Other commonly used threads include various “V” shaped threads, as well as variations in angles of the walls, variations in the shape of the peaks and troughs of the threads.
To summarize, what is needed is a reusable collapsible tube, which can dispense essentially all of its contents. There is a need for reusable collapsible tubes which may be reopened to load the contents, particularly for food containers for use in travel and wilderness settings.